Chlorobenzoates are known to be common intermediates of PCB degradation in microorganisms, hence, any effort to bioremediate PCB-contaminated sites will necessarily have to address the issue of chlorobenzoate metabolism. This project focuses on elucidation of the pathways and enzyme mechanisms for chlorobenzoate dehalogenation systems. Intermediates in the pathways are characterized by a combination of methods including mass spectrometry for samples obtained from whole organisms, cell-free transformation systems, and purified enzymes. In 1995, a reductive pathway for metabolism of 2,4-dichlorobenzoate was established with important information provided by mass spectrometric analyses.